Rebar used in concrete

ABSTRACT

A non-circular rebar used in concrete includes a square rebar, a rectangular rebar, an elliptical rebar, a trapezium rebar, a triangular rebar, and a rebar with round edges and corners. The square, rectangular, elliptical, trapezium, and triangular rebars and the rebar with round edges and corners substitute the conventional circular rebar, so that the rebars can be tied easily to save the space occupied. Since the distance of the resultant force of the tensile stresses of the rebar from the boundary of the concrete becomes smaller or the concrete protecting layer becomes thicker, the change of the shape increases the bonding between the rebar and concrete, and the safety of construction is improved. The non-circular rebar includes a smooth rebar and a ribbed rebar with a non-circular main cross-section.

The current application claims a foreign priority to the patent application of China No. 201310545272.5 filed on Nov. 7, 2013.

FIELD OF THE INVENTION

The present invention relates to the technical field of concretes, in particular to a non-circular rebar used in concrete.

BACKGROUND OF THE INVENTION

In general, rebar refers to rebar or fiber reinforced polymer (FRP) used in concrete, and the rebar usually has a circular cross-section. The rebar includes smooth rebar, ribbed rebar, and twisted rebar, and the there are various types of rebar classified according to chemical composition, production skill, rolling shape, supply form, diameter and usage. For example, the rebar used in steel reinforced concrete refers to concrete with steel bar or steel disc, and it is divided into smooth steel and ribbed steel according to its shape. The steel in the concrete is primarily provided for bearing tensile stresses. Since the rebar includes a rib, the ribbed steel has a greater bonding with the concrete and a better effect of bearing external forces. The rebar is used extensively in various types of concrete structures, particularly for building construction, road and bridge construction, railway construction, and hydraulic engineering construction.

The conventional rebar used in concrete is generally in a circular shape, and thus having the following drawbacks: (1) Since the contact is point-to-point or line-to-line, it is inconvenient to tie the circular rebar. (2) The circular rebar occupies a relatively larger space. (3) The distance of the resultant force of the tensile stresses of the rebar from the boundary of the concrete is relatively greater, or the concrete protecting layer becomes thinner. (4) The bonding between the rebar and the concrete is also smaller.

SUMMARY OF THE INVENTION

To overcome the aforementioned shortcomings of the prior art, the present invention provides a non-circular rebar with the features of simple structure, convenient installation and use, and high working efficiency, and the non-circular rebar no longer has the problems of being tied inconveniently, occupying too much space, having a too-large distance from the resultant force of the tensile stresses of the rebar to the boundary of the concrete or a too-small bonding between the rebar and the concrete.

In a preferred embodiment of the present invention, a non-circular rebar used in concrete has a non-circular main cross-section which substitute the circular main cross-section of the conventional circular rebar, and the rebar is designed to have certain functions and bear forces in certain directions in the concrete structure, and the non-circular rebar used in concrete comprises a square rebar, a rectangular rebar, an elliptical rebar, a trapezium rebar, a triangular rebar, and a rebar with round edges and corners, and the non-circular rebar further comprises a smooth non-circular main cross-section or a ribbed non-circular main cross-section.

Further, the non-circular rebar used in concrete not just includes steel only, but also includes a fiber reinforced composite material such as FRP rebar.

In the non-circular rebar used in concrete in accordance with the present invention, the square, rectangular, elliptical, trapezium, and triangular rebar and the rebar with round edges and corners substitute the conventional circular rebar, so that the rebar can be tied easily to save the space occupied. The distance of the resultant force of the tensile stresses of the rebar from the boundary of the concrete becomes closer or the concrete protecting layer becomes thicker, so that the change of the shape increases the bonding between the rebar and concrete to assure the safety of construction.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a square cross-section of a non-circular rebar used in concrete according to a preferred embodiment of the present invention;

FIG. 2 is a schematic view of a rectangular cross-section of a non-circular rebar used in concrete according to a preferred embodiment of the present invention;

FIG. 3 is a schematic view of a square cross-section of a non-circular rebar with round edges and corners and used in concrete according to a preferred embodiment of the present invention;

FIG. 4 is a schematic view of a rectangular cross-section of a non-circular rebar with smoothened corners and used in concrete according to a preferred embodiment of the present invention;

FIG. 5 is a schematic view of a stack condition when the rebars in different shapes are tied with each other according to a preferred embodiment of the present invention;

FIG. 6 is a schematic view of storing rebars of different shapes according to a preferred embodiment of the present invention; and

FIG. 7 is a schematic view of a concrete protecting layer for rebars of equal cross-sectional area according to a preferred embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will become clearer in light of the following detailed description of an illustrative embodiment of this invention described in connection with the drawings. It is intended that the embodiments and drawings disclosed herein are to be considered illustrative rather than restrictive.

With reference to FIGS. 1 to 4 for a non-circular rebar used in concrete in accordance with the present invention, the non-circular rebar is a rebar with a non-circular main cross-section, and the non-circular shape includes but not limited to a square, a rectangle, an ellipse, a trapezium, a triangle, and any shape with round edges and corners. Some of these shapes are shown in FIGS. 1 to 4, and the round corners is intended to reduce stress concentration in the rebar and to reduce the flow resistance of aggregates and mortars around the rebar during a casting process.

The rebar of the present invention not just includes steel only, but also includes a fiber reinforced composite material such as FRP and any other rebar in concrete. The rebar is provided for industrial and civil constructions including road and bridge, railway, and hydraulic engineering constructions. The rebar includes a smooth rebar and a ribbed rebar (such as a thread rebar, and a herringbone or crescent shaped reinforcement).

The effect of the present invention is illustrated by the following computation and comparison:

In FIG. 5, the circular rebar is in a point-to-point (or line-to-line) contact, so that it is inconvenient to tie the circular rebar. On the other hand, the square rebar is in a plane-to-plane contact, so that it is convenient to tie the square rebar.

In FIG. 6, the circular rebar occupies a larger space, but the square rebar is in a plane-to-plane contact, and thus occupying a smaller space.

In FIG. 7, the circular rebar has a diameter greater than the side of the square provided that their cross-sectional areas are equal. Therefore, the distance of the resultant force of the tensile stresses of the rebar from the boundary of the concrete is greater, or the concrete protecting layer becomes thinner. The circular rebar of the same cross-sectional area has a smaller contact area with the concrete than that of the square rebar, and thus the bonding between the rebar and the concrete is smaller than that of the square rebar.

Assumed that the cross-sectional area of the rebar is equal to A, and if a circular rebar is used, the diameter is equal to

${d = {\sqrt{\frac{4A}{\pi}} = {1.128\sqrt{A}}}},$

and the contacting circumference of the intersected plane between the rebar and the concrete is L_(C)=πd=√{square root over (4πA)}=3.545√{square root over (A)}. If a square rebar is used, the length of its side is equal to a=√{square root over (A)}, the circumference of the intersected plane between the rebar and the concrete will be equal to L_(R)=4a=4√{square root over (A)}>L_(C). In other words, the contact area of the square rebar with the concrete is increased by 12.83% over the circular rebar having the same cross-sectional area, and the bonding between the square rebar having the same cross-sectional area and the concrete is increased by 12.83% over the circular rebar.

Since the length of each side of the cross-section of the square rebar is 12.83% smaller than the diameter d of the circular rebar, so that the thickness of the concrete protecting layer of the rebar is increased by 0.06415 times of the diameter. For example, if the diameter of the circular rebar is 20 mm, and a square rebar is used to substitute the circular rebar, the thickness of the concrete protecting layer is increased by 1.283 mm (as shown in FIG. 7) while other conditions remain unchanged. When the tying of several rebars is taken into consideration, the increase of the thickness of the protecting layer is more significant. If a rectangular rebar is used, the thickness of the protecting layer can be increased more.

When the projected dimension of the cross-sectional area of the rebar is decreased, the distance between the rebars is increased, so that the aggregates and mortars can flow between the rebars easily.

The rebar of the present invention is designed with specific direction and position according to the distributing direction of the forces exerted on the concrete. The rebar of the present invention for a larger rebar (having a diameter greater than 3 mm, and a relatively greater length) including pre-stressing rebar, distribution reinforcement, structural reinforcement and anchoring reinforcement. For example, a main reinforcement and an oblique reinforcement have an effect of bearing a stress and constraining a crack of the concrete, and a hoop reinforcement has an effect of bearing a shear force exerted on components to constraint the main reinforcement, and the concrete primarily bears pressure and shear force. In the present invention, the rebars are tied by fixing the rebars at specific positions of the concrete first, and then casting the concrete in order to enhance the overall bearing capacity and ductility of the components.

The present invention does not include the rebars (such as the steel fiber or composite fiber in concrete) with small size and disordered direction and position and intended for improving the tensile strength, toughness and ductility of the concrete. The fiber in the fiber concrete and the concrete are mixed together by stirring, and its purpose is to enhance the tensile strength, toughness and ductility of the concrete. The diameter of the cross-sectional area of the fiber generally falls within a range of 0.4˜0.7 mm, and the length/diameter ratio is preferably 40˜70 mm.

In summation of the description above, the present invention improves over the prior art, and is thus duly filed for patent application. While the invention has been described by means of specific embodiments, numerous modifications and variations could be made thereto by those skilled in the art without departing from the scope and spirit of the invention set forth in the claims. 

1. A non-circular rebar used in concrete, comprising the non-circular rebar being selected from the group consisting of a square rebar, a rectangular rebar, an elliptical rebar, a trapezium rebar, a triangular rebar, and a rebar with round edges and corners; the non-circular rebar being a smooth rebar or a ribbed rebar with a non-circular main cross-section; the non-circular rebar comprising steel and a fiber reinforced composite material; the non-circular rebar with a non-circular main cross-section substituting a conventional rebar with a circular main cross-section; the non-circular rebar having certain functions and bearing forces in certain directions in a concrete structure; and the non-circular rebar having an enhanced overall bearing capacity and ductility.
 2. The non-circular rebar used in concrete according to claim 1, wherein the fiber reinforced composite material is FRP. 